Saul Kripke

Early Life and Prodigious Beginnings

Saul Aaron Kripke was born on November 13, 1940, in Bay Shore, New York, and grew up in Omaha, Nebraska, in a Jewish family. His father was a rabbi, and his mother a writer. Kripke was a genuine philosophical prodigy: he taught himself ancient Hebrew by age six, read Shakespeare's complete works by nine, and mastered the works of Descartes before entering his teens.

At the age of fifteen (some accounts say seventeen), Kripke wrote a paper on completeness theorems for modal logic that was published in the Journal of Symbolic Logic in 1959, while he was still a high school student. This work provided the first complete semantics for modal logic (possible worlds semantics, now called Kripke semantics), which became the standard framework for the field.

Kripke attended Harvard as an undergraduate, graduating in 1962, and was offered a teaching position at Harvard before completing a Ph.D. — a virtually unprecedented occurrence in academic philosophy.

Possible Worlds Semantics

Kripke's formal work on modal logic provided rigorous semantics for reasoning about possibility and necessity. Kripke models (sets of possible worlds with accessibility relations) gave precise meaning to modal operators and enabled the systematic study of different modal systems (T, S4, S5, etc.). This framework was adopted across philosophy, linguistics, and computer science.

Naming and Necessity (1970/1980)

Kripke's most influential contribution is Naming and Necessity, originally delivered as three lectures at Princeton in January 1970 and published in book form in 1980. The lectures mounted a devastating critique of the dominant Frege-Russell descriptive theory of names, according to which proper names are synonymous with (or abbreviated from) definite descriptions.

Kripke argued that proper names are "rigid designators" — they refer to the same individual in every possible world in which that individual exists. Descriptions, by contrast, are typically not rigid: "the inventor of bifocals" might have referred to someone other than Benjamin Franklin in other circumstances, but "Benjamin Franklin" refers to Franklin in every possible world.

This distinction had dramatic consequences. Kripke showed that identity statements between rigid designators (like "Hesperus is Phosphorus" or "water is H₂O") are, if true, necessarily true — even though they are knowable only a posteriori. This broke the long-assumed equation between the necessary and the a priori, and between the contingent and the a posteriori.

Kripke also defended metaphysical essentialism: objects have some properties necessarily (their origin, their fundamental nature) and others only contingently. Water is necessarily H₂O; it could not have been some other substance. This revived essentialism from its Quinean exile and made it a live option in analytic metaphysics.

The causal theory of reference that emerged from Kripke's arguments (and Hilary Putnam's related work) holds that names are not linked to their referents via descriptions but through causal-historical chains stretching back to an initial "baptism" or dubbing.

Wittgenstein on Rules and Private Language (1982)

Wittgenstein on Rules and Private Language (1982) presented what has become known as "Kripkenstein" — Kripke's interpretation of (and extension of) Wittgenstein's rule-following considerations. Kripke argued that there is no fact about an individual, taken in isolation, that constitutes her meaning one thing rather than another by a word or rule. The "skeptical paradox" is that any finite sequence of uses is compatible with indefinitely many rules. Kripke attributed to Wittgenstein a "skeptical solution": meaning is constituted not by individual mental facts but by community agreement and practice.

The book generated enormous debate about meaning, normativity, and the conditions for rule-following.

Later Career

Kripke held positions at Rockefeller University, Princeton, and the City University of New York (CUNY), where the Saul Kripke Center was established. Much of his work remained unpublished or circulated only as lecture transcripts for decades, leading to a complex relationship between his published and unpublished contributions. He died on September 15, 2022, in Plainsboro, New Jersey.